System and method for an injection using a syringe needle

ABSTRACT

An auto-injector for injecting a fluid medicament into a patient from a pre-filled syringe requires a disposable cassette that is selectively engageable with the reusable injector. The syringe is latched onto the cassette, and the cassette is then engaged with the injector. Activation of the injector causes a first motor to move the syringe so its needle is extended from a concealed position inside the cassette for injection of the medicament. A second motor on the injector is then activated to expel fluid medicament from the syringe. Then, the first motor is again activated to withdraw the syringe into the cassette for disposal of the cassette/syringe after an injection.

FIELD OF THE INVENTION

The present invention pertains generally to systems and methods forinjecting fluid medicaments into a patient from a syringe. Moreparticularly, the present invention pertains to auto-injectors thatconceal the injection needle of a hypodermic syringe before, and afteran injection. The present invention is particularly, but notexclusively, useful as a system and method that employs a bifurcateddrive mechanism wherein one motor moves the entire syringe for aninjection, and another motor moves the syringe plunger for expelling afluid medicament from the syringe.

BACKGROUND OF THE INVENTION

In order to inject a fluid medicament into a patient when using ahypodermic syringe, three separate and distinct tasks must be performed.These are: 1) insertion of the needle into the patient; 2) injection ofthe fluid medicament from the syringe into the patient; and 3)withdrawal of the needle after the injection has been completed. Foreach task, the magnitude and direction of forces on the syringe, as wellas the location of their application, are different from the othertasks. For instance, compare the task of inserting the needle, with thetask of injecting the fluid medicament. Insertion of the needle requiresthat only minimal forces be applied on the syringe, and that they beapplied for only a very short period of time. On the other hand,injection of the medicament requires a much greater force be applied.Further, this force must be applied on the plunger of the syringe forwhat will typically be a relatively longer period of time. In comparisonwith both of these tasks, needle withdrawal requires the application ofa force in the opposite direction. These, and other similarconsiderations, become important when the injection process is to beautomated.

Springs for generating forces on a syringe in an automated process havebeen used heretofore for various purposes. A characteristic of springs,however, is that the magnitude and direction of a spring force are notvariable. Consequently, springs do not lend themselves for so-called“multi-tasking” operations. This is particularly so where precisecontrol over a syringe injection operation is required, and differentmagnitude forces are sequentially required in the same direction (e.g.needle insertion and medicament injection).

In addition to the mechanical considerations mentioned above, the designof an auto-injector also requires “user-friendly” considerations. Inparticular, it is desirable that the injection needle of a syringe beoperationally concealed from the view of a user. Preferably, thisconcealment can be maintained before, during and after an injectionprocedure. Further, it is desirable that operation of the syringe belimited to only those times when the syringe is properly positioned foran injection.

In light of the above, it is an object of the present invention toprovide a two-motor device for performing the injection of a fluidmedicament into a patient wherein each motor generates different forceson a hypodermic syringe for different purposes. Another object of thepresent invention is to provide a reusable injector that can beoperationally engaged with a disposable, pre-filled syringe. Stillanother object of the present invention is to provide an auto-injectorsystem wherein the needle of a pre-filled syringe is operationallyconcealed and the system is operable only when the injector is properlypositioned against the skin of a patient for an injection. Anotherobject of the present invention is to provide a system and a method forautomatically injecting a fluid medicament from a pre-filled syringethat is relatively simple to manufacture, is easy to use and iscomparatively cost effective.

SUMMARY OF THE INVENTION

In accordance with the present invention an autoinjector system includesa disposable cassette that operates in combination with a reusableinjector. Prior to an engagement of the cassette with the injector,however, a pre-filled syringe is mounted and latched onto the cassette.When latched, the syringe is held on the cassette in a so-called “homeposition”. For the present invention, this pre-filled syringe may be ofany type syringe well-known in the pertinent art that has a fluidchamber with an injection needle at its distal end, and a plunger thatcan be advanced into the fluid chamber. When the cassette, with syringe,is engaged with the injector, the system is ready for use.

Operation of the system of the present invention requires two separatemotors that are individually mounted on the injector. Though they aremechanically independent of each other, the respective operations ofthese two motors must be coordinated. Specifically, a first motor isused to effect movements of the entire syringe assembly (i.e. syringechamber, injection needle and plunger are all moved together). On theother hand, a second motor is employed to advance the plunger into thefluid chamber for performing an injection of a fluid medicament.

In a duty cycle of the system, the first motor moves a drive rod intoengagement with the syringe. With this engagement, the drive rod alsoreleases the latch that otherwise holds the syringe in its “homeposition.” After the syringe has been released, the first motor thenadvances the syringe in a distal direction on the cassette. Thismovement inserts the injection needle into a patient. Further, the firstmotor can be used to abruptly stop the needle when a specified needledepth has been achieved. The first motor can then be used to helpstabilize the needle during an injection of the medical medicament fromthe syringe.

As mentioned above, the injection of medical medicament from the syringeis accomplished using the second motor. In detail, once the needle hasbeen properly inserted into the patient, the second motor moves a pusherto urge against the plunger of the syringe to advance the plunger intothe fluid chamber of the syringe. Importantly, the second motor can beprogrammed to advance the plunger into the fluid chamber at apredetermined rate(s) for compliance with an injection protocol.

After the injection has been completed, the second motor withdraws thepusher. The first motor is then used again. Specifically, the firstmotor is now used to withdraw the injection needle from the patient, andto return the syringe to its “home position” on the cassette, where itis re-latched onto the cassette. The cassette can then be removed fromthe injector and discarded.

In order to control the concerted operations of the first and secondmotors, the system includes a microcomputer that is mounted on theinjector. Importantly, the microcomputer operates the motors withdifferent forces, and at different speeds for different purposes. Morespecifically, the first motor must operate quickly to insert the needle(e.g. 0.1 to 1 m/s), but it does not require much force to do so.Similarly, needle withdrawal by the first motor requires a minimalforce. Unlike the first motor, however, the second motor will typicallybe required to generate greater forces for the injection of fluidmedicament. And, accordingly, it will also typically operate at slowerspeeds. Further, and most importantly, different injections (i.e.advancements of the syringe plunger by the second motor) may requiredifferent injection rates. Thus, the second motor requires speed controlprovided by the microcomputer.

Together with the components mentioned above, the system of the presentinvention may, optionally, employ a capacitance skin sensor of a typewell known in the pertinent art. If used, such a sensor will allow theuser to ascertain whether the system has been properly positioned for aninjection. In detail, a metal foil is positioned at the extreme distalend of the injector to establish a capacitance signal whenever the foilis in contact with a skin surface of the patient. The function of thissignal is actually two-fold. First, it can be used to prevent initialoperation, if the system is not properly positioned. And, second, it canbe used to interrupt operation of the system, if it becomes improperlypositioned during an injection.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1 is a perspective view of an autoinjector system showing acassette engaged with an injector in accordance with the presentinvention;

FIG. 2 is an exploded perspective view of the cassette and its componentelements for use with the present invention;

FIG. 3A is a perspective view of a cassette and a drive assembly of thesystem in position at the beginning and at the end of a duty cycle;

FIG. 3B is a view of the components shown in FIG. 3A with the syringe inthe cassette being advanced by a first motor of the drive assembly forinsertion of the syringe needle into a patient; and

FIG. 3C is a view of the components shown in FIG. 3B with the plunger inthe syringe being advanced by a second motor of the drive assembly forinjection of a fluid medicament from the syringe into the patient.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, an autoinjector system in accordance withthe present invention is shown and is generally designated 10. As shown,the system 10 essentially includes a disposable cassette 12 and are-useable injector 14. Further, as shown in phantom in FIG. 1, a driveassembly 16 and a microcomputer 18 are mounted inside the injector 14.As intended for the present invention, the microcomputer 18 is activatedby depression of the button 20 on the injector 14. And, when activated,the microcomputer 18 controls the operation of the drive assembly 16 forits interaction with the cassette 12.

In FIG. 2 it will be seen that the cassette 12 includes a housing 22, asleeve member 24 and a syringe assembly 26. More specifically, thesyringe assembly 26 is of a type well-known in the pertinent art thathas a syringe chamber 28 for holding a fluid medicament. The syringeassembly 26 will also have an injection needle 30, and a plunger 32 thatis moveable within the syringe chamber 28 to expel fluid medicament fromthe syringe chamber 28 through the injection needle 30. FIG. 2 alsoshows that the syringe assembly 26 is formed with an orifice 34 thatallows for contact with the plunger 32 for the stated purpose. Asintended for the present invention, the syringe assembly 26 is fixedlyjoined with the sleeve member 24 and this combination (i.e. syringeassembly 26 and sleeve member 24) is incorporated with the housing 22 toestablish the cassette 12.

Still referring to FIG. 2, it will be seen that the sleeve member 24includes a protrusion 36. Further, it will be seen that the housing 22is formed with a fixation member 38 that is dimensioned for engagementwith the injector 14 (see FIG. 1). As is to be appreciated by theskilled artisan, the fixation member 38 engages with the injector 14 toposition the cassette 12 in an operational alignment with the driveassembly 16. Importantly, the cassette 12 can be fixedly held on theinjector 14 during an operation duty cycle of the system 10, andselectively removed from the injector 14 after its use.

FIG. 2 also shows that the housing 22 is formed with a latch mechanism40. In detail, the latch mechanism 40 includes a pair of opposed,resilient arms 42 a and 42 b that are respectively formed with a detent44 a and 44 b. As shown, the resilient arms 42 a and 42 b straddle aslot 46 that extends along the side 48 of the housing 22.

An important aspect of the present invention involves the assembly ofthe cassette 12 into an integral unit. When assembled, it is to beappreciated that the cassette 12 is intended for use only so long asthere is fluid medicament in the syringe chamber 28 and, it isthereafter disposable. Prior to assembly, the syringe assembly 26 willhave a pre-filled syringe chamber 28 holding a defined dose. Thepre-filled syringe assembly 26 is then inserted into the sleeve member24 where it is fixedly held. Movements of the sleeve member 24 will thusresult in a corresponding movement of the syringe assembly 26. Thecombination (i.e. syringe assembly 26 and sleeve member 24) is thenjoined with the housing 22. When so joined, the protrusion 36 on sleevemember 24 fits in the detents 44 a and 44 b between the resilient arms42 a and 42 b. Accordingly, the syringe assembly 26 is held on thecassette 12 in a so-called “home position”. Importantly, with thesyringe assembly 26 in the “home position”, the injection needle 30 ofthe syringe assembly 26 is held, and concealed within the housing 22. Inthis configuration, the cassette 12 can be engaged with the injector 14substantially as shown in FIG. 1.

For an operation of the system 10, reference is directed collectively toFIGS. 3A, 3B and 3C. Although the injector 14 is not shown in theseFigs., it is to be appreciated that the cassette 12 and the driveassembly 16 are to be considered as being operationally mounted on theinjector 14 (i.e. cross-reference FIGS. 3A, 3B and 3C with FIG. 1).Further, in greater detail, the drive assembly 16 is shown in FIG. 3A toinclude a first motor 50 that is used to move a drive rod 52. Also, asecond motor 54 is shown that is used to move a pusher 56. For purposesof the present invention, the motors 50 and 54 can be of any type wellknown in the pertinent art. Furthermore, the respective movements ofdrive rod 52 and pusher 56 can be provided by any well known mechanicaldevice such as a lead screw or a rack-and-pinion. As noted above, theoperations of the first motor 50 and the second motor 54 are bothcontrolled by the microcomputer 18.

In overview, a duty cycle for the system 10 can be envisioned as aseries of sequential changes in the configuration of cassette 12. Forsystem 10, these configuration changes are caused by separate operationsof the first motor 50 and the second motor 54. In compliance with theseoperations, a complete duty cycle for the system 10 will constitute, inorder, configurations shown from FIG. 3A, to FIG. 3B, to FIG. 3C, andthen in reverse order from FIG. 3C, back to FIG. 3B and FIG. 3A.

FIG. 3A, shows the cassette 12 with the syringe assembly 26 in its “homeposition.” Importantly, in this “home position” the protrusion 36 onsleeve member 24 is held by the latch mechanism 40 on housing 22. And,consequently, the injection needle 30 of the syringe assembly 26 is heldand concealed within the cassette 12. FIG. 3B shows the cassette 12 withthe syringe assembly 26 moved into an advanced position wherein theinjection needle 30 has been extended from the cassette 12 through ahole 58 at the distal end 60 of the system 10 (see FIG. 1). It is to beappreciated that during the movement from FIG. 3A to FIG. 3B, the firstmotor 50 advances the drive rod 52. Specifically, with this advancement,the drive rod 52 interacts with latch mechanism 40 to release protrusion36, and to thereby allow a distal movement of the now “unlatched”syringe assembly 26 and sleeve member 24 on the housing 22.Specifically, this movement is controlled by the microcomputer 18 and isperformed with sufficient force to allow the injection needle 30 topenetrate into the tissue of a patient. Preferably, this movement of thesyringe assembly 26 from the “home position” (FIG. 3A) to the advancedposition (FIG. 3B) is accomplished at a speed of approximately 0.1 to 1m/s. Further, the first motor 50 can be pre-programmed to stabilize thesyringe assembly 26 in its advanced position.

With the syringe assembly 26 in its advanced position (FIG. 3B),microcomputer 18 then activates second motor 54 to move pusher 56against the plunger 32 in syringe chamber 28 (see FIG. 2). Again,microcomputer 18 is in control and, in this case, can be pre-programmedto advance the plunger 32 at an appropriate speed for injection of thefluid medicament from the syringe chamber 28. At the completion of theinjection, the respective configurations of the cassette 12 and thedrive assembly 16 are as shown in FIG. 3C. As mentioned above,completion of the injection duty cycle requires the pusher 56 bewithdrawn. This withdrawal of the pusher 56 is accomplished by thesecond motor 54. Once the pusher 56 has been withdrawn (see FIG. 3B),the first motor 50 is again activated to withdraw the drive rod 52. Thedrive rod 52 then pulls the protrusion 36 back for engagement with thelatch mechanism 40, and the syringe assembly 26 is thus returned to its“home position.” The cassette 12 can then be removed from the injector14 and discarded.

As an additional feature of the system 10, a sensor 62 can be providedat the distal end of the injector 14. In particular, the sensor 62should be positioned adjacent the hole 58 of cassette 12. For purposesof the present invention, the sensor 62 is preferably of a type thatwill react to capacitance that can be measured between the sensor 62 andthe skin of the patient. The purpose of this sensor 62 is to establishthat the system 10 is in physical contact with the patient.Specifically, the microcomputer 18 will operate a duty cycle for thesystem 10 only when such contact is indicated. Otherwise, there can beno operation of the system 10.

While the particular System and Method for an Injection Using a SyringeNeedle as herein shown and disclosed in detail is fully capable ofobtaining the objects and providing the advantages herein before stated,it is to be understood that it is merely illustrative of the presentlypreferred embodiments of the invention and that no limitations areintended to the details of construction or design herein shown otherthan as described in the appended claims.

1. A system for injecting a fluid medicament into a patient whichcomprises: a cassette having a latch mechanism; a hypodermic syringeengageable with the latch mechanism for holding the syringe on thecassette; an injector having a means for selectively holding thecassette on the injector; a first motor mounted on the injector, thefirst motor being engageable with the cassette for selectively latchingand unlatching the syringe from the cassette, and engageable with thesyringe for moving the unlatched syringe on the cassette between a firstposition and a second position; a second motor mounted on the injector,the second motor being engageable with the syringe for expelling thefluid medicament from the syringe; and a computer mounted on theinjector for coordinated control of the first and second motors.
 2. Asystem as recited in claim 1 wherein the hypodermic syringe comprises: asyringe chamber for holding the fluid medicament therein; an injectionneedle extending from the syringe chamber; and a plunger slidablymounted for advancement into the syringe chamber to expel fluidmedicament therefrom through the injection needle.
 3. A system asrecited in claim 2 wherein the first position is characterized by theinjection needle being withdrawn and concealed within the cassette, andthe second position is characterized by having the injection needleextend from the cassette and from the injector for expelling the fluidmedicament from the syringe.
 4. A system as recited in claim 3 whereinthe latched syringe is fixedly held in the first position on thecassette.
 5. A system as recited in claim 4 wherein a duty cyclerequires, in sequence: computer control of the first motor for movementof the unlatched syringe at a predetermined speed from the firstposition to the second position; computer control of the second motorfor advancement of the plunger into the syringe chamber at apredetermined rate for expelling fluid medicament from the syringe; andcomputer control of the first motor for withdrawal of the syringe fromthe second position to the first position and for activation of thelatch to fixedly hold the syringe in the first position on the cassette.6. A system as recited in claim 5 wherein the predetermined speed foradvancement of the syringe from the first position to the secondposition is approximately 0.1 to 1 m/s.
 7. A system as recited in claim3 wherein the cassette is formed with an orifice to allow for extensionof the injection needle from the cassette, and the system furthercomprises a skin sensor mounted on the injector adjacent the orifice togenerate a contact signal whenever the orifice is positioned against theskin of the patient.
 8. A system as recited in claim 1 wherein thecassette further comprises: a cassette body engageable with the holdingmeans on the injector; and a sleeve slidingly mounted on the cassettebody for movement between the first position and the second position,wherein the syringe is fixedly held on the sleeve for movementtherewith, and wherein the latch mechanism includes a first part formedon the cassette body and a second part formed on the sleeve.
 9. A systemfor injecting a fluid medicament into a patient which comprises: ahypodermic syringe having a syringe chamber for holding the fluidmedicament therein, an injection needle extending from the syringechamber, and a plunger slidably mounted for advancement into the syringechamber to expel fluid medicament therefrom through the injectionneedle; a support means for holding the syringe, with the syringe beingselectively moveable on the support means between a first positionwherein the injection needle is withdrawn and concealed within thesupport means and a second position wherein the injection needle extendsfrom the support means for expelling the fluid medicament from thesyringe; and a drive means engaged with the support means, the drivemeans being bifurcated to have a first motor for moving the hypodermicsyringe on the support means and a second motor for advancing theplunger into the syringe chamber to expel the fluid medicament when thesyringe is in the second position.
 10. A system as recited in claim 9wherein the support means comprises: a cassette; and a latch mechanismformed on the cassette for holding the syringe in the first position.11. A system as recited in claim 10 wherein the cassette comprises: acassette body engageable with the holding means on the injector; and asleeve slidingly mounted on the cassette body for movement between thefirst position and the second position, wherein the syringe is fixedlyheld on the sleeve for movement therewith, and wherein the latchmechanism includes a first part formed on the cassette body and a secondpart formed on the sleeve.
 12. A system as recited in claim 10 whereinthe first motor is engageable with the cassette for selectively latchingand unlatching the syringe from the cassette.
 13. A system as recited inclaim 10 further comprising a computer mounted on the drive means forcoordinated control of the first motor and the second motor.
 14. Asystem as recited in claim 13 wherein a duty cycle requires, insequence: computer control of the first motor for movement of theunlatched syringe at a predetermined speed from the first position tothe second position; computer control of the second motor foradvancement of the plunger into the syringe chamber with a predeterminedforce at a predetermined rate for expelling fluid medicament from thesyringe; and computer control of the first motor for withdrawal of thesyringe from the first position to the second position and foractivation of the latch to fixedly hold the syringe in the firstposition on the cassette.
 15. A system as recited in claim 14 whereinthe predetermined speed for advancement of the syringe from the firstposition to the second position is approximately 0.1 to 1 m/s.
 16. Amethod for injecting a fluid medicament from a syringe into a patientcomprises the steps of: engaging a hypodermic syringe with a cassette,wherein the cassette has a latch mechanism for holding the syringe onthe cassette and the syringe includes a syringe chamber for holding thefluid medicament therein, an injection needle extending from the syringechamber, and a plunger slidably mounted for advancement into the syringechamber to expel fluid medicament therefrom through the injectionneedle; holding the cassette on an injector, wherein the injector has afirst motor engageable with the cassette for selectively latching andunlatching the syringe from the cassette, and engageable with thesyringe for moving the unlatched syringe on the cassette between a firstposition wherein the injection needle is withdrawn and concealed withthe cassette and a second position wherein the injection needle extendsfrom the cassette, and a second motor engageable with the syringe forexpelling the fluid medicament from the syringe when the syringe is inthe second position, and a computer mounted for coordinating control ofthe first and second motors; and activating the injector to perform aduty cycle for an injection of medicament from the syringe.
 17. A methodas recited in claim 16 wherein a duty cycle comprises, in sequence, thesteps of: control of the first motor for movement of the unlatchedsyringe at a predetermined speed from the first position to the secondposition; control of the second motor for advancement of the plungerinto the syringe chamber with a predetermined force at a predeterminedrate for expelling fluid medicament from the syringe; and control of thefirst motor for withdrawal of the syringe from the first position to thesecond position and for activation of the latch to fixedly hold thesyringe in the first position on the cassette.
 18. A method as recitedin claim 17 wherein the predetermined speed for advancement of thesyringe from the first position to the second position is approximately0.1 to 1 m/s.
 19. A method as recited in claim 16 further comprising thestep of monitoring the activating step wherein the cassette is formedwith an orifice to allow for extension of the injection needle from thecassette, and a skin sensor mounted on the injector adjacent the orificeto generate a contact signal for determining when the orifice ispositioned against the skin of the patient.
 20. A method as recited inclaim 16 wherein the cassette comprises a cassette body engageable withthe holding means on the injector, and a sleeve slidingly mounted on thecassette body for movement between the first position and the secondposition, wherein the syringe is fixedly held on the sleeve for movementtherewith, and wherein the latch mechanism includes a first part formedon the cassette body and a second part formed on the sleeve.